1. Field of the Invention
The present invention relates to a thin film device provided with a thin film coil of a solenoid type.
2. Description of the Related Art
In recent years, a thin film device including a thin film coil of a solenoid type is widely used in the electronic equipment field of various applications. One example of such thin film devices includes a thin film inductor, which is a circuit element having inductance (for example, reference to Patent Documents 1, 2). The thin film inductor has such an advantage that inductance value can be increased compared with a case where a spiral thin film coil is used.    [Patent Document 1]    Japanese Laid-Open Patent Publication (Kokai) No. H05-029146    [Patent Document 2]    Japanese Laid-Open Patent Publication No. 2004-296816
In the thin film devices represented by the foregoing thin film inductor, it is necessary to reduce parasitic capacitance generated in the thin film coils in order to set up a frequency band, which is usable as operating frequency, to a higher range. If parasitic capacitance is large, resonance frequency will fall and the Q factor will decrease. The “Q factor” is a numeric value for quantitatively indicating a performance of coils mounted in a resonance circuit and so on, generally expressed with a definitional equation Q=ωL/R. Here, ω, L, and R respectively represent an angular velocity, inductance, and resistance at a frequency applied.